The present invention relates a method and system for measuring the increase in compressive strength/bearing capacity for the soil which serves as a foundation for earth-supported structures such as buildings, roadways, pavements, and airport facilities.
Such earth-supported structures require that the underlying soil have sufficient bearing capacity to support the weight of the structure as well as the additional weight exerted onto the structures during usage (live loads). In order to design a stable and durable structure, an accurate assessment of bearing capacity is required.
The bearing capacity of the underlying soil is not always sufficient for the intended structure's design and use. Therefore, remedial measures to increase the strength/bearing capacity of the soil system is required. The resulting increase in bearing capacity due to the remedial method of injecting a stabilizing agent into the underlying soil mass may be determined using this invention.
Existing structures may also experience differential deflection or settlement due to unconsolidated soil strata, water infiltration, decomposition of organic materials, void conditions, poorly executed site preparation during original construction, additional live loads, soils consolidation from on-site vibration caused by equipment or traffic operations, et cetera. Such problems can be corrected by increasing the compressive strength of compromised soils. Until the present invention, there was no way to efficiently and accurately monitor the increase in soil strength/bearing capacity during remediation by soil injection.
Various conventional systems for remedial stabilization and/or lifting to correct structural settlement (including driven piles, piers, segmented cylinder piles, micro-piles, and other systems) rely on transfer of structural weight to deeper, more solid soils or rely on the skin friction between soils and the exterior surface of the pile itself to increase load-bearing capability. Such construction systems are invasive, disruptive, time consuming, and often unsuitable for pavements, lightweight slab, and other applications.
Conventional stabilization and/or lifting systems also include the method originally described in U.S. Pat. No. 4,567,708, which entails the injection of a polymeric material beneath a built structure to fill voids and to create a expansive force from the increase in volume caused by the chemical reaction of the polymeric substance. This system did not address the need for soil remediation as indicated by measurement of increased confined soil strength at depth.
Conventional stabilization systems also include the method described in U.S. Pat. No. 6,634,831, which is incorporated by reference herein in its entirety, and which entails the injection of a material through holes or tubes into the soil to produce compaction of the contiguous soil. This method requires constant surface monitoring to detect the exact moment at which the soil or the structure begins to lift upward. This system does not address the need to continuously measure and monitor, at depth, the amount of improved compaction of the targeted soil. This system does not monitor unknown and unexpected migration of the injectable material away from the injection site creating unexpected surface lifting some distance away from the desired location.
The “Method for Reducing the Liquefaction Potential of Foundation Soils” (PCT Application TR2003/000083 dated Nov. 5, 2003) also teaches the strengthening of soils using expansive polymers as indicated only by surface testing of the project's structural slab, using “laser beams,” which are presumed to be laser leveling systems. Such measurement fails to monitor and measure the precise confined soil strength at depth.
According to the Geotechnical Policy and Procedure manual produced by the Nebraska Department of Roads, a pressuremeter test may be used to determine the pressure at which the soil fails for a given depth. However, this test fails to be useful in determining the confined soil strength at a particular depth, and fails to provide a way to document evidence of confined soil pressures gained from the injection process.
The previously discussed patents teach only to monitor the surface for evidence of movement to indicate a sufficiency of injection material and soil strength. The previous systems fail to provide a system of monitoring and control in situ at depth and do not measure the differential, real-time increase in confined soil strength as the expanding polymer is introduced. The previous systems do not provide a means to document the strength gained from the injection process. Rather, the previous systems rely on monitoring for movement at the surface as a sort of proxy for what is occurring in the soil.
Previous methods have not met the need of providing in situ real-time soil strength data at various soil depths. Thus, previous methods also fail to indicate when geotechnical engineering specifications have been met or exceeded.